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Which of the following statements is true?
a Explanation: The electric field is the cross product of the velocity and the magnetic field intensity. This is given by Lorentz equation.
a
See lessExplanation: The electric field is the cross product of the velocity and the
magnetic field intensity. This is given by Lorentz equation.
Find the force due to a current element of length 2cm and flux density of 12 tesla. The current through the element will be 5A.
b Explanation: The force due to a current element is given by F = BI x L. Thus F = 12 x 5 x 0.02 = 1.2 units.
b
See lessExplanation: The force due to a current element is given by F = BI x L. Thus F = 12 x 5 x
0.02 = 1.2 units.
Find the displacement current when the flux density is given by t3 at 2 seconds.
c Explanation: The displacement current is given by Jd = dD/dt. Thus Jd = 3t2. At time t = 2, we get Jd = 3(2)2= 12A.
c
See lessExplanation: The displacement current is given by Jd = dD/dt. Thus Jd = 3t2. At time t =
2, we get Jd = 3(2)2= 12A.
Calculate the emf when a coil of 100 turns is subjected to a flux rate of 0.3 tesla/sec.
c Explanation: The induced emf is given by Vemf = -dλ/dt = -Ndψ/dt. Thus emf will be -100 x 0.3 = -30 units.
c
See lessExplanation: The induced emf is given by Vemf = -dλ/dt = -Ndψ/dt. Thus emf will be -100
x 0.3 = -30 units.
The induced voltage will oppose the flux producing it. State True/False.
a Explanation: According to Lenz law, the induced voltage acts in such a way that it opposes the flux producing it. This is indicated by a negative sign.
a
See lessExplanation: According to Lenz law, the induced voltage acts in such a way that it
opposes the flux producing it. This is indicated by a negative sign.
According to Faraday’s law, EMF stands for
d Explanation: The force in any closed circuit due to the change in the flux linkage of the circuit is called as electromotive force EMF. This phenomenon is called as Faraday’s law.
d
See lessExplanation: The force in any closed circuit due to the change in the flux linkage of the
circuit is called as electromotive force EMF. This phenomenon is called as Faraday’s
law.
For time varying currents, the field or waves will be
c Explanation: For stationary charges, the field is electrostatic. For steady currents, the field is magneto static. But for time varying currents, the field or waves will be electromagnetic.
c
See lessExplanation: For stationary charges, the field is electrostatic. For steady currents, the
field is magneto static. But for time varying currents, the field or waves will be
electromagnetic.
Find the magnetic field when a circular conductor of very high radius is subjected to a current of 12A and the point P is at the centre of the conductor.
c Explanation: The magnetic field of a circular conductor with point on the centre is given by I/2a. If the radius is assumed to be infinite, then H = 12/2(∞) = 0
c
See lessExplanation: The magnetic field of a circular conductor with point on the centre is given
by I/2a. If the radius is assumed to be infinite, then H = 12/2(∞) = 0
The magnetic field intensity will be zero inside a conductor. State true/false.
b Explanation: Electric field will be zero inside a conductor and magnetic field will be zero outside the conductor. In other words, the conductor boundary, E will be maximum and H will be minimum.
b
See lessExplanation: Electric field will be zero inside a conductor and magnetic field will be zero
outside the conductor. In other words, the conductor boundary, E will be maximum and
H will be minimum.
In a static magnetic field only magnetic dipoles exist. State True/False.
a Explanation: From Gauss law for magnetic field, we get divergence of the magnetic flux density is always zero (ie, Div(B) = 0). This implies the non-existence of magnetic monopole.
a
See lessExplanation: From Gauss law for magnetic field, we get divergence of the magnetic flux
density is always zero (ie, Div(B) = 0). This implies the non-existence of magnetic
monopole.